Figure 3. Relationship of the time constants for the two components of [K⁺]_o recovery, τ_fast and τ_slow, to the magnitude of activity-dependent changes in [K⁺]_o and to stimulus duration.

A, [K⁺]_o transients from three different nerves in response to a 1 s, 100 Hz stimulus at 37 °C. The early phase of [K⁺]_o recovery accelerates with increases in the size of the evoked [K⁺]_o increase. B, time constants of [K⁺]_o recovery from 21 nerves following a 1 s, 100 Hz stimulus plotted against the peak increase in [K⁺]_o produced with each stimulus. τ_fast became shorter as a function of Δ[K⁺]_o. The linear fit to τ_fast had a slope of −0.24 with a regression coefficient of 0.96. τ_slow was minimally affected by the magnitude of Δ[K⁺]_o. The linear fit to τ_slow had a slope of −0.08 with a regression coefficient of 0.38. C, decay phases of [K⁺]_o following a 1 s (•) and a 10 s (○) stimulus train from a representative nerve. Simulations of the individual exponential components of post-stimulus recovery of [K⁺]_o are plotted on the same graph. The amplitude and τ of the fast component, but not the slow component, were unaffected by stimulus duration. D, time constants of [K⁺]_o recovery (means ±s.d.) versus stimulus duration. τ_slow increased with stimulus duration but τ_fast was relatively invariant. Numbers in parentheses indicate the number of nerves each data point represents.